This invention relates in general to the construction of filters and in particular to a new and useful electrostatic filter for floating particles which includes a folded dielectric filter material made of fiber with a metallic vapor deposit thereon.
Modern high efficiency filters for floating particles, made of fiber material, will remove from the air or other gas flow conducted through them, floating materials like dust, smoke and mists of different grain size. According to the pertinent regulations, the minimum degree of separation must be 99.97%. This applies to particles 0.3 .mu.m in diameter. Despite the space between the fibers in the filter material, smaller particles are retained also. Among others, electrostatic forces within the filter material, generated either by the flow of the air or gas to be purified or by accessory equipment, are responsible for the retention of the particles in the filters.
One known electrostatic filter cell consists of a corrugated, air-permeable web of dielectric filter material, enclosed by a frame made of nonconducting material, usually cardboard. One side of the web is provided with an arrangement of conducting strips such as of aluminum or silver, applied by printing or spraying. The strips are parallel, equispaced and insulated against each other. At opposite edges of the web the strip ends are alternately interconnected via extended areas, resulting in two comblike groups whose teeth engage each other. Through contact pieces at the faces of the frame a dc voltage of opposite polarity is applied to both groups (German AS No. 14 07 019). However, in operation a bridging of the insulating gaps between the strips can occur due to conductive dust deposits, eventually leading to flashovers.
In another electrostatic filter cell, a corrugated, dielectric filter material web is also disposed in a cardboard frame. The electrostatic field is obtained through an electrically conducting material applied in the form of strips to the combs of the corrugated filter material web. The application of a voltage of opposite polarity to the opposite outsides of the filter cell generates the electrostatic field through which the efficiency of the floating particles filter is improved (French Pat. No. 11 07 132).
Disadvantageously there is the free area between the conducting strips through which small quantities of the floating particles can pass.